This invention relates to an apparatus and method for six-sided board painting.
In manufacturing operations that produce millwork such as moldings, sills, frames, etc., it has been the practice to vacuum paint the workpiece on an assembly line. The stock is put in a bin and each piece is fed onto a conveyor line, with the pieces abutting each other end to end along the conveyor. Each piece enters a vacuum painting apparatus, where paint is sprayed onto the piece under a vacuum. The piece then exits the apparatus onto another conveyor to be dried and heat-treated.
In order to paint each piece on six sides, that is, the top, bottom, sides, and ends, it is necessary to keep each piece slightly separated from the following piece. If this were not done, the paint would not be able to reach the trailing end of the lead piece or the leading end of the following piece. Industry practice has been to insert a staple in the trailing end of the lead piece to separate this piece slightly from the following piece. When the boards have been painted, the staples must be removed.
Inserting and removing staples is a time-consuming, labor-intensive, potentially health-damaging operation. The constant twisting, gripping movement of removing the staples can cause such ailments as carpal tunnel syndrome.
In addition, the staples caused a partial loss of vacuum within the vacuum painting chamber because the boards were spaced apart as they entered the chamber. The gap between the boards caused a partial loss of vacuum because the seals of the vacuum painting chamber could not close tightly around the boards. This partial loss resulted in reduced painting efficiency and waste of paint. There are also environmental concerns if paint escapes from the vacuum chamber into the surrounding air.
Another earlier solution to the problem of painting the ends of the boards is the optional vacuum take-away system offered by Advanced Manufacturing and Development (AM&D) of Willitz, Calif. This system causes parts to separate in the application chamber, allowing the ends to be coated. However, the inventor has found that this vacuum take-away system leaves undesirable streaks on the boards. Indeed the operator'manual for this system states that the belts of the conveyor will cause transfer marks to the bottom side of the part when the bottom is being painted. The inventor has also found that this vacuum take-away system cannot operate well near the maximum speed of the conveyor.
There is a need for an apparatus for six-sided painting of parts such as boards, moldings, sills, and frames that allows the ends of the parts to be painted in a vacuum painting system and is adjustable for part size (length and width) and the speed of the conveyor.